1. Field of the Invention
The present invention relates to the field of keratometers, and more particularly, to the field of scanning keratometers.
2. Prior Art
There are various instances in which a precise mapping of the surface of the human eye is desirable. These can range from simple diagnostic examinations to precise measurements for custom fitting contact lenses, to pre and post surgical cornea mapping.
Several techniques are currently being used for measuring the surface of the eye. The most common technique used in the majority of clinical applications is the standard keratometer. Concentric circles of known diameters (pitch) are projected onto the surface of the eye. The reflected patterns are then studied and compared for any nonconcentricity in the reflections. The shapes however, are sampled a limited number of times, usually with less than ten points being taken and documented. These points are sometimes taken manually, and at other times taken automatically as in the Humphrey automated keratometer. Nevertheless, due to the low number of samples, the measurement is by necessity low in resolution, incurring the imprecision of needed extrapolation from point to point. Thus choosing a contact lens is similar to choosing a pair of shoes. The customer receives a general overall fit, and hopes that any inaccuracies are absorbed in the system. If the proper fit is not accomplished, then the patient must suffer through the discomfort of poorly fitting lenses.
The Humphrey automated keratometer is disclosed in U.S. Pat. Nos. 4,407,572 and 4,420,228. Other patents disclosing keratometers include U.S. Pat. Nos. 3,781,096; 4,019,813; 4,157,859; 4,159,867; 4,429,960; and 4,440,477.